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<title>SYMBOLS</title>
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 <h1>SYMBOLS</h1><br>
 <p>
  The best way to understand how a symbol is defined is to analyze an existing one. 
  Load a test schematic (for example <kbd>test.sch</kbd>). Let's consider the
  resistor symbol. Use the <kbd>Insert</kbd> key to place the <kbd>devices/res.sym</kbd> symbol.
 </p>
 <img src="xschem_insert.png">
 <p>
  Use the file selector dialog to locate <kbd>res.sym</kbd>.
 </p>
 <img src="building_symbol_01.png">
 <p>
  Now select the resistor by left-clicking on it (it will turn to grey color) 
 </p>
 <img src="building_symbol_02.png">
 <p> 
  After selecting the component (component is an instance of a symbol)
  descend into its symbol definition
  by pressing the <kbd>'i'</kbd> key. XSCHEM will load the
  <kbd>devices/res.sym</kbd> file and show it in 
  the drawing window. Before descending it asks if you want to save
  the parent schematic drawing 
  before loading the resistor symbol. Answer 'yes'.
 </p>
 <img src="building_symbol_03.png">
 <p>
  The image above is the 'symbol definition', you can now select individual graphic elements that 
  represent the symbol, lines, rectangles and text.
  Normally a symbol contains some pins, these are just rectangles drawn on the 'pin' layer, and some 
  graphics / descriptive text. Another fundamental part of symbols are properties.
  Properties are text strings that define attributes of the symbol, for example: 
 </p>
 <ul>
  <li>The name of the connection pins</li>
  <li>The type of the symbol (spice primitive, subcircuit, documentation)</li>
  <li>The format of the spice/verilog/VHDL netlist for the symbol</li>
 </ul>
 <p>
  We will return on symbols after explaining properties.
 </p>
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